Skip group 0002 unless it is part of query.
Skip group 0002 unless it is part of query.

Since these DICOM tools were meant to be used for files, they allow
group 0002 to be part of the query.  However, if group 0002 is not
part of the query, then we can save some CPU cycles by not reporting
any group 0002 attributes.

dgobbi/vtk-dicom,dgobbi/vtk-dicom,dgobbi/vtk-dicom